High resolution, high intensity cathode ray tube

ABSTRACT

This invention relates to a radiation display tube having an increased image resolution and recording efficiency and comprising a first evacuated chambers, a second chamber having a radiation transparent end wall with a conductive inner surface and which is adapted to be filled with an ionizable gas of desired constituency and pressure, and a gas tight, nonconducting interface wall positioned therebetween and having a plurality of discrete conducting elements extending therethrough. Apparatus is provided in the first chamber for projecting and scanning an electron beam upon the interface wall which thereby causes a current to be conducted through the interface whereby a sequence of arc discharges will occur in the second chamber. Means are also provided to vary the fill of the second chamber with gas of the desired constituency.

[451 Oct. 16, 1973" HIGH RESOLUTION, HIGH INTENSITY CATHODE RAY TUBE Jon W. Ogland, Glen Burnie, Md.

Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed: July 24, 1972 Appl. No.: 274,700

Inventor:

Assignee:

US. Cl. 315/31 R, 315/30, 313/82 BF, 250/49.5 E, 250/495 TE Int. Cl. I-I0lj 29/56 Field of Search 315/12, 30, 31 R; 313/68 R, 82 BF, 82 T; 250/49.5 E, 49.5 GC, 49.5 C, 49.5 TC, 49.5 TE; 178/7.5 D

OTHER PUBLICATIONS Gas Discharge Display Device, IBM Tech. Disc. Bull.,

Vol. 12, No. 12, May 1970, p. 2,324.

Primary Examiner-Benjamin R. Padgett Assistant Examiner-P. A. Nelson Attorney-F. 1-1. Henson et a1.

[5 7] ABSTRACT This invention relates to a radiation display tube having an. increased image resolution and recording efficiency and comprising a first evacuated chambers, a

second chamber having a radiation transparent end wall with a conductive inner surface and which is adapted to be filled with an ionizable gas of desired constituency and pressure, and a gas tight, nonconducting interface wall positioned therebetween and having a plurality of discrete conducting elements extending therethrough. Apparatus is provided in-the first chamber for projecting and scanning an electron beam upon the interface wall which thereby causes a current to be conducted through the interface whereby a sequence of arc discharges will occur in the second chamber. Means are also provided to vary the fill of the second chamber with gas of the desired constituency.

4 Claims, 2 Drawing Figures BEAM DE FLECTION L Hoavfit I "1. w

r 4 .8 1' ER I8 19 o A 2 6/ L. 1 D I-9 elf FL r 24 22 '1 SIGNAL I e if e e BRIGHTNESS FOCUS I CONTROL CONTROL {I wwvwv -wiM 3 Q\ v 6 6 34 32 POWER HIGH SUPPLY 4 |2- VOLTAGE SUPPLY PATENTEB UN 1 6 I975 SIG NA L INPUT BRIGHTN CONTROL HIGH RESOLUTION, HIGH INTENSITY CATHODE RAY TUBE CROSS REFERENCES TO RELATED APPLICATIONS So far as known, this invention is not related to any pending patent application.

BACKGROUND OF THE INVENTION The cathode ray tube has been found to be a most desirable means for producing a visual display or for the recording of information on photographic media, because of the availability of a high resolution or number of information elements per unit area. However, use of a light source produced from a conventional phosphor coated screen has been found undesirable for certain recording applications. Because of the crystalline nature of the phosphor, the light produced is scattered at the crystal surfaces and the resulting spot of light produced on the screen is several times larger than the thickness of the existing electron beam resulting in a corresponding loss of resolution. Another disadvantage is low efficiency when recording emissions of certain wave lengths as in the ultraviolet range, for example. The recording efficiency has been further reduced by the lack of an available very fast ultraviolet sensitive film which is required when employing a phosphor coating in a CRT envelope.

Such deficiences, as those just described, are particularly undesirable for the recording of radar information on photographic or photochromic films. It would therefore be more desirable to substantially improve the image resolution and recording efficiency by combining the advantages of high resolution electron beam operation and the high efficiency light generated by a discrete gas discharge while eliminating the inherent problems caused by utilizing a phosphor, and at the same time, providing simultaneous control over the brightness and color intensity of the display.

PRIOR ART The following patents disclosed a display tube which can photographically record or display electron images and that also include an evacuated chamber in which a wall is employed that has a plurality of transversely extending and electrically conducting fine wires therethrough:

Sabah Hicks However, neither of the above patents shows a radiation display tube having a first evacuated chamber, a partition wall, and a second gas tight chamber that is adapted to be filled with an ionizable gas so that an arc discharge may occur in a gas confined to a closed space while also permitting the constituency and pressure of the gas therein to be varied.

SUMMARY OF THE INVENTION chamber has a tight and radiation transparent end wall that is spaced from and opposes the interface wall. The inner surface of the opposing end wall is radiation transparent and electrically conductive and is to be connected to a source of potential. This end wall may also be provided with a plurality of transversely extending discrete radiation transmitting fibers therein. Disposed within the first chamber is associated apparatus for projecting and scanning an electron beam onto the interface wall, thereby causing a current to be conducted therethrough and a sequence of arc discharges to occur in the second chamber between ends of the electrically conducting elements of the interface and the conductive inner surface of the chamber end wall.

Means are also provided to vary'the fill of the second chamber with an ionizable gas of desired constituency so that the color and intensity of the image may be controlled simultaneously with and during their recording of the display.

BRIEF DESCRIPTION OF THE DRAWINGS present invention adapted to be used for the recording of a radiation display on photographic media.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, a radiation display tube 1, such as a cathode ray tube modified inaccordance with the instant invention, is shown having two enclosed chambers. The first chamber 2 isevacuated, and the second chamber 3 is adapted to be filled with an ionizable gas of desired constituency and pressure. A gas tight interface wall 4, composed of an electrically insulating material, is positioned between chambers-2 and 3 and is secured to-the tube envelope by any suitable means, such as by a fused glass to metal seal 7. Arranged within interface wall 4 are a plurality of discrete, electrically conducting elements6s'uch'as fine metal filaments or wires that, form agrid and extend transversely through the interface. The useand fabrication of conductive elements disposed transversely within an insulating wall memberor face plate has been well known in the art and is exemplified in U.S. Pat. Nos. 2,015,570 and 3,240,987.

Gas filled chamber 3 includes a radiation transparent and gas tight end wall 8 which may serve as the tube face plate while opposing interface wall 4 and being spaced thereform. The gas filled space comprising chamber 3, or that area defined between interface 4 and opposing wall 8 is generally narrow to help eliminate the dispersal of radiation generated therein which can cause a corresponding loss of image resolution. A more complete description of the optimum specifications for chamber 3 and the ionizable gases which may be supplied thereto will follow. The inner surface 9 of end wall 8 is covered with a radiation transparent and electrically conductive coating 10. By way of example, inner surface coating 10 may be either a'NESA (tin oxide) or a fine metal mesh coating. The coating 10 is placed at a high positive voltage with respect tothe'grid containing the conductive elements 6. In the assembled relationship, coating 10 is electricallyconnected to oneterminal of a source of high voltage 12 and thereby serves as an anode for the display tube while replacing the conventional non-transparent phosphor coated anode.

Apparatus is disposed in the first compartment 2 and is adapted to be electrically connected to signal source 15 and to a power supply 14 for generating and projecting an electron beam onto interface wall 4. A basic schematic is illustrated as but one example of an electrical circuit for energizing both anode l and the beam generating apparatus. The beam generating apparatus generally includes an electron gun 16 for generating and causing an electron beam to impinge upon wall 4 and a beam deflection system 23 for regulating the beam scanning. Electron gun 16 is of the conventional type, having a cathode 17, which is connected in the circuit with power supply 14 and to the opposite terminal of high voltage source 12, a signal electrode 21, and focusing electrodes 18, 19, and 20. Beam deflection system 23 comprises well known vertical and horizontal deflection plates 22 and 24 respectively to be connected to their sweep voltage sources (not shown). Similarly, instead of an electrostatic beam deflection (as shown), it can be appreciated that conventional electromagnetic beam deflection means, such as a magnetic yoke (not shown) surrounding display tube 1, may also be suitably empioyed.

When an electron beam, shown diagrammatically at 28, is generated and caused to impinge upon interface wall 4, the fine wire grid will assume a potential with respect to anode 10. The conductive elements or fine wires 6 disposed in wall 4 which comprise the grid are not connected to any source of potential, but, when individually actuated by the beam 28, act merely as a discrete electrical conductor arranged as part of a respective series circuit for conducting a stream of electrons between electron gun 16 and anode 10. After a discrete wire 6 has been energized by electron beam 28, an electrical current will be conducted therethrough and into the gas filled compartment 3 to ionize the gas, and by scanning the electron beam, a series of radiation generating arc discharges will be caused to occur in that region between the respective ends of conducting wires 6 and the conductive coating of the inner surface 9 of end wall 8. Thus, the radiation point sources generated from the arc discharges in gas filled chamber 3, may be viewed as a trace from the outside of the display tube transparent end wall or face plate 8 with an increased image resolution while providing simultaneous control of the brightness and color intensity over that of conventional CRT display tubes, because no phosphor coatings have been employed for generating the source of light.

Means 30 are also provided to vary the fill in chamber 3 with an ionizable gas of a desired constituency in order to change the color of the display or to increase the efficiency when recording the image (explained more fully with reference to FIG. 2) on photographic or photochromic films, such as when recording radar information. Means 30 for carrying desired gas into chamber 3 include a tube 32, which extends into chamber 3 and a valve 34, which is connected to tube 32 and is adapted to be connected to a source of gas (not shown) under pressure. Although only one fill varying means 30 is shown, it is within the scope of this invention to have a plurality of fill means and sources in communication with chamber 3 that could permit chamber 3 to be similtaneously filled with gas of a first constituency while gas of a second constituency already within the chamber could be removed therefrom, thereby permitting an effective control over the choice of any desired spectrum of light emission.

The gas filled second chamber 3 may be operated ei ther at pressures in the range 1 to 10 millimeters mercury, which give the characteristics of a low pressure gas discharge, or at pressures in the range 500 to 1,000 millimeters mercury, which give the characteristics of a high pressure gas discharge. In the former, the light emission will consist of sharply defined spectral lines. In the latter, the light emission will consist of a more or less continuous spectrum of varying intensity having peaks at difference wavelengths.

The region wherein an arc discharge occurs is quite narrow, i.e., the distance between the interface wall 4 and the conductively coated face plate 8 is made as short as permissible for adequately sustaining the arc discharge, Depending on the gas pressure chosen, the spacing may be less than one or up to a few millimeters.

The gas may be either pure, for example neon, which emits orange-red light in the wavelenth region 5,400 to 6,400 Angstroms, or nitrogen, which emits yelloworange light in the wavelength region 5,667 to 5,680 Angstroms. As an alternative, the gas may be a mixture of, for example, argon and neon. The color of the light will be determined mainly by the gas component having the lower excitation potential, in this case by argon. It has four lines between 6,965 and 8,115 Angstroms, or which the latter is the strongest, however, being in the infrared, only the other three are visible.

The gas may also be composed of, for example, a noble gas and a metal vapor such as sodium, mercury, or copper. The color of the light emission is, in this case, determined only by the metal, since its excitation potential is far lower than that of the noble gas. Even so, the latter cannot be omitted because the vapor pressure of the metals at room temperature is far too low to sustain and gas discharge alone. The noble gas serves as an ignition agent, and as such has an important function, and greatly multiplies the number of collisions between the electrons and the metal atoms.

A mixture of argon and neon of a few millimeters pressure plus a small amount of sodium emits strongly in the yellow at 5,890 and 5,896 Anstroms. This emission falls near the most sensitive region of human vision, and, in addition, the electrical to light conversion is highly efficient, in excess of 50 percent. With a small amount of mercury instead of sodium, the main emission falls in the ultraviolet and, in particular, very strongly at 2,537 Angstroms. Although not visible, this emission is very useful for its actinic effect. Thus, it is very effective for recording on photochromic films. For this application, the type of glass chosen for the face plate has to transmit the ultraviolet light without undue absorption.

Using copper to provide the metal ions, in conjunction with a noble gas, gives emission in the ultraviolet in the range of 3,248 to 3,274 Angstroms, and weaker in the visible blue-green range of 5,106 to 5,218 Angstrorns. These gases and metals are given only as examples. The physics handbooks contain the emission spectra for all the known elements.

Referring to FIG. 2 of the drawings, the radiation display tube of FIG. 1 may be further modified to not only increase the image resolution but to increase the efficiency with which the image may be recorded onto a photographic media. The transparent end wall or face plate 48 of the gas filled second chamber 43 of tube 41 is provided with a plurality of transversely extending, discrete radiation transmitting fibers 52. The fibers 52 may be what is well known in the art of optics as fiber optics. The fiber optics have been found to minimize the scattering of light generated from the arc discharge in the second chamber 43 and passing directly through the face plate to expose an external film source (not shown), thus helping to increase the recording efficiency. A suitable fastening means, such as a metal weld 47 can be sufficient to join face plate 48, the interface wall 44, with a discrete conductive element 46 embedded therein, and that portion of the tube which forms the first evacuated chamber 42. A radiation transparent conductive coating 50, similar to that described in FIG. 1, may cover the inside surface 49 of face plate 48 so as to serve as an anode in the assembled relationship. The projection and scanning of an electron beam from associated apparatus within evacuated chamber 42 to interface wall 44, the generation of a series of arc discharges in chamber 43, and the means 60 to vary the gas fill of chamber 43 are also similar to those previously disclosed in reference to FIG. 1 and will therefore not be discussed herein further detail.

The instant invention can therefore be employed as either a radiation display tube for observing an electron trace or as an improved means of recording the trace on a photographic media without the need of special, ultraviolet sensitive films. Means have also been provided to allow control of the brightness, color, and intensity of the image simultaneously with an optimization of resolution and recording efficiency. Other modification will occur to those skilled in the art.

I claim:

1. A radiation display tube comprising a first evacuated chamber, a second chamber adapted to be filled with an ionizable gas having a desired constituency and pressure, a gas tight interface wall of electrically insulating material between said first and said second chambers, a plurality of discrete electrically conducting elements extending transversely through said interface wall, said second chamber having aradiation transparent and gas tight wall opposing said interface wall and spaced therefrom, the inner surface of said opposing wall being radiation transparent and electrically conductive to be connected to a source of potential, and means disposed in said first chamber and adapted to be electrically connected to an electrical signal and to the source of potential for projecting and scanning an electron beam onto said interface wall, thereby causing radiation generating arc discharges to occur in said second chamber and between respective ends of said electrically conducting elements and said inner conductive surface of the opposing wall, said are discharges being visible through the transparent opposing wall.

2. The invention of claim 1, wherein means are provided to vary the fill of said second chamber with gas of desired constitutency, said means including at least one tube extending into said chamber, and a valve connected to said tube and adapted to be connected to a source of gas under pressure to provide means for carrying the gas from said source through said valve totransmitting fibers. 

1. A radiation display tube comprising a first evacuated chamber, a second chamber adapted to be filled with an ionizable gas having a desired constituency and pressure, a gas tight interface wall of electrically insulating material between said first and said second chambers, a plurality of discrete electrically conducting elements extending transversely through said interface wall, said second chamber having a radiation transparent and gas tight wall opposing said interface wall and spaced therefrom, the inner surface of said opposing wall being radiation transparent and electrically conductive to be connected to a source of potential, and means disposed in said first chamber and adapted to be electrically connected to an electrical signal and to the source of potential for projecting and scanning an electron beam onto said interface wall, thereby causing radiation generating arc discharges to occur in said second chamber and between respective ends of said electrically conducting elements and said inner conductive surface of the opposing wall, said arc discharges being visible through the transparent opposing wall.
 2. The invention of claim 1, wherein means are provided to vary the fill of said second chamber with gas of desired constitutency, said means including at least one tube extending into said chamber, and a valve connected to said tube and adapted to be connected to a source of gas under pressure to provide means for carrying the gas from said source through said valve to vary the fill.
 3. The invention of claim 1, wherein the discrete electrically conducting elements extending through said interface wall are metal filaments.
 4. The invention of claim 1, wherein the radiation transparent wall of said second chamber includes a plurality of transversely extending, discrete radiation transmitting fibers. 